I used to think that not being able to move a joint meant a broken bone, but then my son broke his wrist playing football. His wrist hurt and was slightly swollen but he could still use it and bend it. He even kept on playing with it, saying it hurt but wasn’t too bad. I was very surprised because usually he is a real wuss about pain.
However, it didn’t get better over the next several days so we went to the doctor and got an X-ray. Yup, sure enough, it was broken! Like @gailcalled, he broke the distal end of the radius, but unlike her he had no black and blue marks, his wrist wasn’t distorted, and it hurt but not as much as we would have expected.
In other words, if you think it might be broken or if it doesn’t get better within a few days, get an X-ray. In any case, if it really, really hurts, don’t wait. Go ahead and get the X-ray.